The present invention relates to a wick roller for use in the fuser section of a electrophotographic copier/printer machine and in one of its aspects relates to the journals, affixed in each end of a wick roller, for mounting the wick roller in the fuser section of an electrophotographic machine and the method of affixing said journals to the wick roller.
In a typical electrophotographic machine (e.g. copier, duplicator, printer, etc.), a continuous loop of photoconductor film is commonly used to transfer an inputted image onto a receiving medium (e.g. a sheet of paper). The film is initially charged and the desired image is projected onto the charged film. Next, a toner is applied to the charged image and the toner image is then transferred onto the sheet of paper or other medium. The paper now passes through a fuser section where the toner is fixed to the paper by elevated temperature and pressure. This latter step is typically accomplished by passing the paper between a pressure roller and a fuser roller, one of which is heated.
Unfortunately, however, when the paper passes between the rollers, some of the heat-softened toner particles often adhere to the surface of the fuser roller, resulting in what is known as xe2x80x9coffsetxe2x80x9d. As is well understood in the art, toner offset can adversely affect the quality of the copies being made by the machine. A common way to alleviate xe2x80x9coffsetxe2x80x9d is to apply a silicone oil (hereinafter referred to a xe2x80x9crelease oilxe2x80x9d) onto the fuser roller to prevent the toner from sticking thereto.
To apply the release oil onto the fuser roller, it is common to use a xe2x80x9cwick rollerxe2x80x9d. A typical wick roller is comprised of a cylindrical, permeable ceramic core covered with a layer of a high temperature, wicking material (e.g. felt or the like). The release oil is typically supplied through a thin, perforated conduit that, in turn, is positioned within an axial bore in the ceramic core whereby the oil is distributed evenly along the wick roller. The oil permeates through the ceramic core and into the wicking layer. The wick roller is periodically moved into and out of contact with the fuser roller so that the release oil is transferred to the fuser roller at timed intervals during the copying operation.
Since the wick roller has to serviced from time to time, it is important that the roller be easily removeable/replaceable. To facilitate this procedure, journals, which form the axle of the roller, are glued or otherwise affixed to each end of the ceramic core and the bearing surfaces on the journals are merely laid into open brackets that, in turn, are pivotably mounted in the fuser section. The loosely-mounted, wick roller only rotates when the brackets are moved to bring the wick roller into contact with the rotating fuser roller
While this type of wick rollers can easily be removed for servicing, unfortunately, a relatively high number of these rollers have experienced early failure in the field. Investigations have revealed that most, if not all, of these early failures occur when the adhesive bond between the journals and the core fails and one or both of the journals break loose and separate from the ceramic core. It is believed that the failure in the adhesive bond is caused primarily by the alternating thermal stresses that occur during the heating and cooling cycles within the fuser section.
As will be appreciated by those who depend on electrophotographic machine(s) in their commercial operations, downtime and costs are a primary concern. Therefore, it can be seen that it is important to extend the operational life of any component, i.e. wick roller, wherever possible, so that the maintenance/service of that component is kept to a minimum.
The present invention provides a wick roller for use in a fuser section of an electrophotographic machine and a method for assembling same wherein the operational life of the wick roller is significantly increased. That is, the journals of the present invention, are significantly less likely to separate from the core of the roller during operation than were the journals used with this type of prior art, wick rollers.
Basically, the construction of the journals of the present invention allows adhesive to be applied both to a journal and to the core, itself, thereby providing a significantly better bond between the two. In known, prior art wick rollers, adhesive is not applied to the core but is applied only to the journal since it has been found that the journal will displace some of the adhesive off the core as the journal is moved into the core. This displaced adhesive will collect in the central bore of the core and can seriously interfere with the positioning of the oil-distribution tube therein.
More specifically, the present invention relates to a wick roller for use in the fuser section of an electrophotographic machine wherein the roller is comprised of an elongated, cylindrical core made of a permeable ceramic material. The core has a central, axially-extending bore therethrough adapted to receive an oil distribution tube for supplying a release oil to the wick roller. The core also has two, axially-extending, cylindrical chambers; one opening from either end of the core with each being adapted to receive a journal therein.
The journals of the present invention are preferably made of plastic and are of basically the same construction. Each journal has a small diameter, bearing surface and a larger diameter, axially-extending, mounting section. The diameter of the mounting section is substantially equal to the diameter of the chamber in which it is to be mounted so that there will be a minimum of clearance therebetween when assembled. An axially-extending, nose section is affixed to the leading edge of the mounting section; preferably formed integrally therewith. The diameter of the nose section is less than that of the mounting section whereby the nose section forms a reduced-diameter, cylindrical step which leads the mounting section into the chamber when the journal is moved into said core.
The reduced-diameter of the nose section provides a xe2x80x9ccatch spacexe2x80x9d for any adhesive that may be displaced (i.e. skived off) from the chamber wall as the journal is forced into the chamber. By allowing any displaced adhesive to collect onto this step, excess adhesive can be applied to both the journal and the chamber wall without the risk that some of the displaced adhesive will foul the central bore of the core.
The mounting section of each journal is provided with a plurality of axially-extending grooves that, in turn, define a plurality of axially-extending ribs. It is desirable to maximize, as far as possible, the number of ribs (e.g. 12) on each mounting section in order to increase the effective contact area between a journal and its respective chamber in the core. By applying adhesive to the outer arcuate surfaces of the ribs and filling the grooves with adhesive and also applying adhesive to the chamber wall, a superior bond can be effected between the journal and the chamber in the core once the journal has been assembled into the chamber and the adhesive has been allowed to set.